"Mr. Speaker, Members of the House, I shall be brief, as I have rather unfortunately become Prime Minister right in the middle of my exams."
— Pitt the Younger, Blackadder the Thirdnote This is only a slight exaggeration — the actual William Pitt the Younger became Prime Minister at the ripe old age of 24.
The Teen Genius is just that: a genius who happens to be a teenager. This character is responsible for coming up with the magical answer to any given episode's problem, while at the same time being generally angsty and teen-like. May be exposed to discrimination by those that don't know him, because he's Just a Kid.
Oddly, the Teen Genius will not normally have any of the odd behavioral quirks of the TV Genius, even if the series lasts long enough to let him mature into an adult.
On a show with an ensemble cast, the teen genius is usually included as a (generally misguided) attempt to appeal to a teen audience. On a show with a teenaged Competence Zone, this is about the only way for the Five-Man Band to include the requisite Smart Guy.
A Teen Genius may sometimes also be Book Dumb, despite the apparent contradiction. A female Teen Genius may be a Genius Ditz. A younger version is the Child Prodigy.
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Theresa "Tessa" Testarossa, Sagara Sōsuke, and Kaname Chidori from Full Metal Panic!. In fact, all Whispered are Teen Geniuses, as they are all exactly the same age to within three minutes. There's a reason for this.
Hakuron from Haou Airen is a top hitman in the Triads and pretty much the heir to his group... at the very early age of 18/19. His companions are hinted to have been this in the past as well.
Mizuno Ami/Sailor Mercury from Sailor Moon, she's always at the top of the ranking in tests and is rumored by other students to have an IQ of 300 (The Sera Myu musicals treat the latter as fact, not a rumor)
All the main characters in Death Note. Except maybe L, who's in his twenties when the events of the series take place, and Misa, who's a Genius Ditz.
Light is an especially egregious example—words can't describe his level of thinking.
Naruto has Shikamaru Nara who has an IQ over 200. He's so smart that everything seems boring to him. Also Itachi Uchiha who had done everything from reaching the very top of his career (Anbu Captain), to joining the most powerful criminal organization as a spy by the time he was only 13 years old. Kakashi Hatake and Minato Namikaze (who would later on become the Fourth Hokage) were also teen geniuses when they were young.
Orochimaru, too. The ninja world has a lot of geniuses, which is to say prodigies. Over 50% of them go violently bananas.
Sakura Haruno deserves a mention in this category for passing the first Chuunin exam test, which was deliberately designed to be so difficult as to force the participants to cheat, simply by understanding the questions and working out the answers. She was the only test-taker shown to pass without cheating, which is saying something considering that one of said test-takers was the aforementioned Shikamaru.
While it is not mentioned very often in the anime, Asuka from Neon Genesis Evangelion has already graduated from college at the age of fourteen, making her a candidate for this trope. She's only in high school in Japan to improve her Japanese due to how bad she is at writing/reading it. While Asuka never really uses these skills in the plot itself, they are quite important for her Character Development (c.f. the whole of "Magma Diver"); they don't affect the plot because all the brains in the world won't help you stop the apocalypse.
In Rebuild, she's a different kind of genius. Instead of college she joined the military becoming the "Pride of the Euro Airforce" and reaching the rank of Captain by age 14. Which might be a little more useful against apocalypses.
Thomas/Touma Norstein in Digimon Savers, and, to a (much) lesser extent, Koushirou "Izzy" Izumi and Ken Ichijouji in Digimon Adventure 02. (With Koushirou as a former Child Prodigy, even.)
Due to his age, Ken is more a Child Prodigy than this trope. However, his Dead Older Brother Osamu very probably counts.
17-year-old Shin'ichi Kudo and Heiji Hattori in Detective Conan both have vast amounts of knowledge and mental abilities superior to most of the adults around them. Shiho Miyano, on the other hand, led The Syndicate's lab before she's 18. This trope tends to be somewhat obscured in Shin'ichi and Shiho's cases by the fact that they spends most of the series in even younger bodies, thus giving them the appearance of Child Prodigies.
In the sister series, Magic Kaito, both Kaito Kuroba/Kaitou Kid and Saguru Hakuba also qualify as this.
Chiyo-chan from Azumanga Daioh, though a Child Prodigy who starts 10th grade at the age of 10, technically becomes a Teen Genius when she graduates from high school at 13.
Irina Woods from Mai-Otome. In addition to her normal Otome duties, she also studies engineering and computers, and is very good friends with Professor Youko.
Ryu Amakusa, Megu Minami, and Kyuu Renjou (though he's more of a Genius Ditz) from Detective Academy Q. Their other teammates, Kazuma Narusawa and Kintarou Touyama, are respectively the Child Prodigy and the Badass Normal.
Trowa"No Name"Barton of Gundam Wing. The other guerrilla Gundam pilots also probably qualify, but he's the only one who manages to infiltrate Oz, probably because unlike the other four boys he doesn't have a massive case of Chronic Hero Syndrome to screw things up for him.
Wu Fei, oddly enough, is apparently their intellectual, followed by Quatre, who's the best military mind among them. Heero has a flair for tactics, although he also acts dumb as a post sometimes. In terms of practical knowledge, they're all extraordinary.
Wu Fei was a college graduate at age 14, as shown in the prequel manga "Episode 0". Also, according to the end notes, had the war not happened and his wife died to defend their home colony he would have probably become a Mad Scientist.
Relena Peacecraft. She's mostly an Ordinary Highschool Student at first, but with some more prodding she becomes the sponsor of a school and later... the Queen of the World.
Actually, the Gundam metaseries has several of these. Amuro Ray and Kamille Vidan were gifted Gadgeteer Geniuses at age 15 and 17, with Kamille even being well-known as an amateur engineer which is vital when he actually designs the Zeta Gundam itself.Judau Ashta piloted his mecha at age 14 (a little younger than the Wing boys), and Usso Ebin straddles the line between this and Child Prodigy got his's at age 13 (Justified Trope: he was trained by his parents beforehand).
Haman Kahn is all but stated to have been one, too. At age 16 she was put in hcarge of the Axis Zeon leadership and became the caretaker of little Mineva Lao Zabi. At age 20, she has become The Chess Master and a foe to fear.
The most recent examples are from Gundam AGE: first-generation!Flit Asuno and his grandson Kio from the third generation. Flit was 14 when he built his Gundam from the blueprints left by his dead mother, Kio began piloting when he was 13 (though in a subversion, his grandpa had been sort-of training him via the videogames that he brought for the kid.)
In Starship Operators, even you're a veteran tactician, you do not mess with Shinon Kouzuki. Trust us, it's a very bad idea fighting her.
Uryuu Ishida is the top academic performer in a 300-strong year group with Bunny-Ears Lawyer tendencies. When he fought Mayuri, who had spent decades studying Quincies and their powers, Mayuri observed that his abilities were way beyond what he'd expect of a 15 year-old...in fact he used some techniques Mayuri had never even heard of before and one-shotted Mayuri and his bankai with a single arrow. It's been made clear by Uryuu's father, Ryuuken, that Uryuu's power still underdeveloped, meaning that what we saw was only a fraction of his real ability.
Orihime Inoue is the third best academic performer in Uryuu's year group and a full-blown Ditzy Genius. She also has spiritual powers that may directly manipulate space-time, which are so unusual and have so much potential that Aizen was interested. So unusual, and so much potential, that Aizen kidnapping her was enough for Soul Society to mobilize against him. It's been stated that the limit of her ability is defined by what she believes she can do with it.
Toushirou Hitsugaya is approximately 13 years old (biologically speaking) and famous as a Shinigami Child Prodigy. Most shinigami can never obtain bankai but Hitsugaya is the youngest person to learn it in the history of Soul Society. However, his power is not fully developed and he lacks the experience of other captains and their emotional maturity (he still sometimes acts like a child trying to do an adult's job). Nevertheless, Kyouraku (one of the oldest and most powerful captains) has said that Hitsugaya will probably surpass him in the next 100 years.
In the Everything but the Rain flashback arc, Uryuu's father Ryuuken seems to be a Teen Genius as well. Even Aizen admits that Urahara is the smartest person in the series, but Ryuuken, as a mere human teenager, is able to follow Urahara's thought processes well enough to startle him into praising the boy.
In Get Backers, most of the major characters are this. Though two extreme examples that have been countlessly lampshaded are Ban Midou and Makubex. Ban has been called a brilliant genius in fighting (though, according to his witch grandmother, "worthless in everything else") ever since he was a kid, and is currently the strongest character in the entire series. And Makubex is a 13 year old computer genius that other characters constantly claim is a Teen Genius.
Hiruma Youichi, who first learned poker from American soldiers stationed in Japan. After losing the first hand, he figured out the rules without anyone telling him and proceeded to gamble his way to taking all of the soliders' money. By high school, he can count cards in blackjack and earn a ridiculous profit. Has managed to figure out a way to get blackmail material on nearly everyone in the country, and many outside the country.
Subverted in the World Cup arc when it's made clear that even with all their abilities, most of the talented players in the series still aren't quite at the NFL level yet (though they're still incredibly talented for the high school and possibly college level).
All members of Spartoi in Soul Eater (not just Maka's group, but Ox's) most of which are in their mid-teens. Both random Shibusen members and senior staff acknowledge them as 'elite', though this status is certainly helped by the numberofunusual powers they possess.
While several characters of Hayate the Combat Butler are 13 and thus between this trope and Child Prodigy Hinagiku is 16 and thus qualifies for this one, as does Athena (supposedly).
The school the story takes on thrives on this trope, it's year-end exam is given in German.
Huey Laforet of Baccano! was a Teen Genius in 1705.
With the cream of the crop gathering and being filtered on every floor of the Tower of God, these are bound to show up. Special attention goes to Koon, who bends the rules at every turn and corner and uses experienced administrators in his schemes, and Baam, whose inherent talent for magic borders to Power Copying.
Zera from Litchi Hikari Club is a certified genius at the age of 13. His sanity may be questioned but he came up with a thinking machine that somehow runs on litchi fruits, his chess skills are superb. More, the prequel shows that in elementary school he constructed a robot all by himself which makes him a Child Genius too. Dentaku is also very smart, he programmed Litchi. And against all odds Jaibo may also qualify. For the most part he acts like the psychotic pretty boy but he did manage to frame the original members of the club in such a way so as to completely fool Zera. Unfortunately his pyschotic tendencies boycot his intelligence.
Bulma Briefs around the time of Dragon Ball is this, particularly when it comes to machinery. She built the Dragon Ball Radar at age 15-16, without any leads and only with her hands and own knowledge, basically kicking off the events of the whole series. Also runs in the family, with her future son Trunks from Dragon Ball Z, who while a teen utilized Time Travel to inform the Z-fighters of the events that led to a Crapsack World. (And using a time travel machine that Bulma herself built before dying in that Bad Future, too.)
Gohan counts too, seeing as he's always been a scholarly type, especially through his teenage years.
In Haruhi Suzumiya, Kyon, despite being a Book Dumb archetype, solves many problems that involves supernaturalities and practically omnipotent organizations, only with his wit and social skill. Even he doesn't hold a candle to, however, Itsuki Koizumi, aka the founder and the leader of The Organization.
Ciel of Black Butler is this trope after he turns thirteen; prior to that, he was a Child Prodigy. His ability to track down the most evil people in London at the behest of the queen while building an extremely successful corporation puts him firmly in the genius category.
Rei Kiriyama from Sangatsu no Lion was (and still is, being a high schooler) a teenage prodigy in shogi, becoming a professional player in middle school as only the fifth person to have done so.
Galilei Donna: Hozuki Ferrari, thirteen-year-old builder of a collapsible rocket scooter that doubles as an overpowered stun gun, goldfish themed airship, goldfish-themed holographically-projected AI...
Kill la Kill: In his third year of middle school, Houka Inumuta could hack into the world's tightest security system just as a self-imposed challenge.
Naru of Ghost Hunt definitely embodies this trope, especially once you learn that he is actually acclaimed parapsychologist Dr. Oliver Davis, meaning he has a doctorate from Oxford at seventeen.
Suzu of Seitokai Yakuindomo is noted to have an IQ of 180, speaks 5 languages and can do 10-digit computations in no time. Ahino and Aria share some of these traits, but they're more of the Ace type.
There's a ludicrous number of teen geniuses in Marvel right now. Amadeus Cho is probably the smartest, but there's also David Alleyne/Prodigy of the Young X-Men, Victor Mancha of the Runaways and Jonas/Vision II and Kate Bishop/Hawkeye II of the Young Avengers. And that's even without including the ghost of Alex Wilder (Runaways again) and the currently MIA Kristoff Vernard von Doom.
Mr. Fantastic, who not only is the biggest nerd in the world and a Rubber ManBadass Bookworm, but was attending university at age 14 and by the time he turned 20 had several science degrees under his belt.
Hiro Okamura from The DCU. He builds a composite robot to save the world from a kryptonite meteor, and Batman states that Hiro's smarter than him.
This is made even more evident in the movie Superman / Batman: Public Enemies.
Peter Parker, a/k/a Spider-Man. Although, after 40 years and with all his smarts, Peter's still taking pictures for the Daily Bugle.
Then he stopped doing that and went to work for Horizon Labs, putting that brain of his to work.
Though never directly shown, Dumbledore, Voldemort, Grindelwald, McGonagall, Lily Potter (née Evans), Severus Snape, and the Marauders (who became Animagi by their fifth year at Hogwarts!) are all implied to have been Teen Geniuses in their own times.
Fred and George Weasley may have earned three OWLs each, but they are capable of advanced magic and become successful businessmen after dropping out of Hogwarts... at 18 years old. While Percy is a pompous Jerkass, he had to have been pretty smart to have become Junior Assistant to the Minister of Magic... also at 18 years old. Though that whole 18 years old thing may be justified, as we never read even a single mention in the series about any Wizarding Colleges.
Astrid Ellison (Resident base breaker of the GONE series) Has a IQ of over 150, can quote whole passages of classical literature (Including Dickins, Shakespeare, Hemingway, Bronte) and learnt to read aged two...Did we mention she's only 14 when first introduced? She's more a literary and book-based genius than a scientific or mathematical one, though.
While we're on that series, Computer Jack is just twelve and he's handling all of the FAYZ's tech issues.
All children of Athena in Percy Jackson and the Olympians , although most notably Annabeth Chase (who starts off a child prodigy but evolves into a teen genius in book 2). She is a archaeological based genius, who knows of every great building in the world along with its exact measurements, perimeter, area, when and by who it was built, and its historical significance. She also possesses an adept talent for general knowledge, being able to answer every question the Sphinx asks her in book 4 and complaining that it was too easy, while the rest of the rather intelligent group couldn't answer one question.
She is such an insanely smart architect that the literal GODS made her Olympus's official architect. She builds palaces for divine beings. That's how badass smart she is.
Artemis Fowl. Technically not a teen in the first book, since he was twelve then, though he gets older later on. And he is smart, to say in the least.
Practically every single character in the Ender’s Game series of novels. Spooky geniuses.
Definitely justified, because that's what the Battleschool program was specifically looking for.
In the Garrett, P.I. series, Kip Prose is a teen inventor, with a head full of ideas for things that hadn't yet been developed in his world (pencils, tricycles). Subverted in that he got his first batch of ideas from aliens sky elves, rather than dreaming them up from scratch.
James H Schmitz's Telzey Amberdon starts out as Star Honor student at the planet's top law school at age 15, before she is Touched by Vorlons. Then again, the student body of Pehanron College seemingly isn't much older than Telzey is; her roommate Gonwil is 19, but she's in her last year, while Telzey still has several years to go. It's either a prep academy for nothing but Teen Geniuses, or the Hub's education system is a tad accelerated. Telzey is still the top student in her year, that's true.
In The Maze Runner Trilogy, it sounds like most of the kids were something of one, but Thomas and Teresa take the prize. Most of them are not seen in action, though, making their genius something of an Informed Ability.
Dime Novel character Johnny Brainerd and The Steam Man of the Prairies. Most likely the Ur Example, predating even Frank Reade and Tom Swift, circa 1868. Earliest example of an "Edisonade," a kind of proto- Steampunk.
All Enid Blyton's Boarding School novels seem to have a handful of these characters. St Clare's has Felicity's musical genius and the almost Sue-ish Lucy Oriell who is perfect at everything, especially art. Malory Towers has even more - even in-story Irene's talent for maths and music is called "genius", Mavis has the voice of an opera singer at the age of fourteen or fifteen, and no-one can match Belinda's drawing skills.
Beatrice Löwenström in "Överenskommelser" is still a teenager at the start of the story, and yep, she's very intelligent. Kind of justified as she was the daughter of a University professor, who had given her a good education and encouraged her to be intelligent.
Illiana Henriksdotter in "Betvingade" is still a teenager as well, and a brilliant medicine woman.
The original TV movie version of Bryce was completely unlikable and a bona fide villain but the version from the TV version is one of the most likeable examples of this trope, in large part because he was depicted as a normal teenage boy who happened to be a genius. The TV series Bryce could be a Ditzy Genius at times and had much the same sense of humour as any 15-year-old boy. He could just do cooler stuff.
A less common example would be Quinn Mallory from Sliders, who, although not a teen at the time of the series, falls under the category by virtue of being young, brilliant, and angsty.
River Tam from Firefly, who is seventeen years old and makes her brother Simon (who was in the top three percent of his class at an elite medical school) look like an "idiot child" by comparison — or so Simon says. Also, she can read minds. The angst factor comes from the fact that she's crazy as a result of cruel medical experimentation done to her at the Academy.
Rose from Power Rangers Operation Overdrive was this in the backstory, but by 18 years old, she was already out of Harvard and working in a university in London. If she's 18, she's technically still a teenager.
Also Dr. K in Power Rangers RPM. She starts with "abducted into government think tank by age 6" and goes from there (she's about 18 at the time of the series).
LOST contains a former Teen Genius: Daniel Faraday was a professor at Oxford and doing time travel experiments by the time he was 19 and he had already graduated sometime in his early to mid teens-explicitly said to be the youngest ever graduate. Then he did said experiments on his own girlfriend, something that went so badly that Oxford wiped any record of him ever having taught there-and by the time we meet him, he's 27 and has memory problems so bad he needs a constant caretaker.
NCIS has an episode with a whole group of teen "analysts" who are practically playing Ender’s Game in real life.
Caprica: Zoe Graystone was raised by two parents who were both brilliant scientists, her father a roboticist and her mother a plastic surgeon. She topped them both by creating an artificial intelligence in her own image at the age of 16.
Claudia from Warehouse 13, and painfully aware of it too. Her brother Joshua is her role model for this behavior.
Dr. Spencer Reid from Criminal Minds is a former Teen Genius and Child Prodigy. He graduated high school when he was 12 and graduated college when he was 16. He was 23 (turned 24 in the fourth episode) when the series began and Hotch mentioned that he was already working at the FBI for three years. In season 6 he complained about not being allowed to drive when he was in college.
A surprising number of students at the Beacon Hills High School on Teen Wolf qualify for this trope. Stiles is extremely intuitive and exhibits a wide breadth of knowledge on many topics. Lydia is a brilliant chemist, and also knows both archaic and classical Latin (and probably other languages as well). Danny is a skilled hacker and knows how to write software. Matt is a photography/videography expert.
Interestingly, in each of these cases there's something of a catch though. Stiles has ADD, meaning he's smart but struggles to focus, Lydia hides her IQ to avoid Intelligence Equals Isolation (and also seems to lose a chunk of mental stability with each season, Danny has a juvenile delinquent record for hacking something he shouldn't have, and Matt turns out to be a stalker and a serial killer. Sort of. It's complicated.
Merlin, the titular character, from Merlin. To others, he appears to be clumsy, incompetent and unintelligent, but Merlin is probably the most intelligent, quick and wise character on the entire show.
The 80s sitcom Head of the Class was about a classroom full of these, learning socialization skills from their ex-hippy teacher.
In A.N.T. Farm the ANTs are part of the Advanced Natural Talents, or ANT, scheme which allows gifted middle-school kids to go to High School several years early. Each child is talented in one particular direction, however: music, art, computers, an eidetic memory and so on. In Real Life of course it's unlikely that their talents alone would allow them to skip grades. The ANTs are TeenGeniuses in their individual specialism but not in a more general sense.
Lady Gaga wrote her first ballad at thirteen and has been writing music for other artists since the age of fifteen, after having been a piano prodigy.
Aphex Twin first started making music by tinkering with his ZX81 home computer at the age of 11, and if the title Selected Ambient Works 85-92 is telling the truth he was already creating his first album by 14.
Jason Becker could play and write blues at 13; and by the time he was 16, he was able to write songs like this. To give an idea of how advanced he was, Jeff Loomis (who is an immensely-skilled and widely celebrated guitarist in his own right) had to practice "Perpetual Burn" for months and somehow nailed it one day through sheer dumb luck. Loomis is in his forties. Becker was NINETEEN when he recorded it.
For that matter, Loomis himself. At the age of sixteen, he managed to get an audition with Megadeth after Jeff Young left and failed to get the job SOLELY because Mustaine felt that he was too young and had too little life experience to be able to handle the rigors of being in an international touring band.
In Mexico, Lucha Libre facilitates this with a stricter weight class than say, that country north of the boarder, allowing teens who can go to make a name for themselves early and advance through the ranks if they have growth spurt. Rey Mysterio Jr made his debut at 14, for example.
Cheerleader Melissa was actually training and working behind the scenes at shows on the road and her uncle's training school while she was still in high school, completing most of her classes by emailing her teachers. She had her first match on her 17th birthday.
Matt Sydal got his wrestling license at age 17, even though his state normally requires you to be 18 before you can apply for one. This would be the basis for a running gag in his Gateway Championship Wrestling career, where he would constantly have his age exaggerated.
Implied example in WSU icon Alicia, who known for pulling fast ones on (almost) the entire promotion. The story was she had shown these tendencies since she sought out a wrestling school at 13.
Britani Knight got an early start in the wrestling business at 13, when she was put on the card of a WAW show because a scheduled wrestler could not make it. She started her career in earnest as a pseudojobber at 14 and was holding gold by 15.
Sexy Juliette The Huntress debuted at age 15 and was considered one of the better wrestlers of the Caribbean before she turned sixteen, earning a contract with the International Wrestling Association and program with Amazona, a rookie of 17 at the time who was getting over surprisingly quickly.
Ertai, from the "Weatherlight Saga" of Magic: The Gathering; subverted when he's captured and transformed into a half-mechanical monstrosity who hates his former friends. Squee (not thatSquee), the young goblin cabin boy, is also a genius by goblin standards, though by human standards that amounts to "merely functioning".
Ciel of Mega Man Zero created Copy-X, a near-perfect duplicate of ThomasLight's greatest work, when she was six years old and devised a completely new energy source before she'd finished her teenage years. ZX's backstory indicates she also created the biometals sometime after the Zero series, and on top of everything else she's a Hot Scientist to boot. Girl gets around, doesn't she?
Tron Bonne certainly counts. Aside from the fact that she created the 40 Servbots, most of the machines she makes are made from spare parts, such as a train and Bruno in the first game. She was 13 in the first game (and her spinoff) and 14 in the second.
Coco Bandicoot from Crash Bandicoot was a tech-genius well before her teenage years.
Rebecca Chambers from Resident Evil had graduated from college and joined up with the elite S.T.A.R.S. police force as a medic by the time she was eighteen, and William Birkin became Umbrella Corp's top scientist at sixteen.
Dmitri and Reese of Backyard Sports are younger than teenagers, but they fit the trope.
Sion Eltnam Atlasia from Melty Blood, talking about a beautiful young teenage girl who can quickly think, she has a mind processing skill equal to that of a supercomputer and can even predict your moves hours or even days before you move. Wow! A super teen genius.
Rita from Tales of Vesperia, occasionally to a ludicrous extent. Despite her age she's probably the most intelligent person in the world by a fair margin; her response to a request for a device that would break most known natural laws is essentially, "It'll take until breakfast at least."
Sachi, one of the heroines of Sharin No Kuni, is explicitly said to have an IQ of 140, is a prodigy-level painter, and something of a math wiz. She pales in comparison to the protagonist, Kenichi, who's in the final stages of what amounts to government sponsored ubermensch training, which means he has a college level education already, as well as having a resume of accomplishments that'd be impressive for a person of any age. He can expound on complicated concepts at the drop of a hat and has to consciously tone himself down so as not to be an Insufferable Genius.
In Fallout 3, player character (a 19-year-old) can be this if you use XP right.
In fact, with high-intelligence and the right perks, one of the first things the player can do literally moments after leaving the Vault is offer to defuse the nuclear bomb that lies in the centre of Megaton.
Grunt from Mass Effect 2 is an odd example. He was genetically engineered to be the ultimate Krogan Super Soldier, being taught via implanted memories and rapidly aged whilst in the tank. Although he's only a few minutes old when Shepard decants him, he's biologically a teenager, who also happens to possess the intelligence of dozens of millennia-old Krogan Warlords. Naturally, in his spare time, Grunt likes reading Hemingway and playing with action figures.
All the teen-aged fighters in The King of Fighters have elements of this, but of note is The Protagonist Kyo Kusanagi. He's said to have properly dominated his pyrokinetic powers and surpassed his father's own skills when he was 15 years old (which is also the time when his Big Brother Mentor and cousin Souji almost lost himself to his darker side and thus asked Kyo to replace him as the family leader). Then, he became the winner of the All-Japan Martial Arts Tournament at age 18, and the Team Japan leader at age 19. The rest is history.
A subtler example is Yuri Sakazaki. She only started training when she was 16-17, and yet she mastered the basics and low techniques of the Kyokugenryu Karate within a year. She didn't stop there, but started imitating other people's techniques as seen above - and developed her own. (Like the infamous Hyakuretsu Binta and her own Super Special, the Hien Hou-oh Kyaku.)
The biggest one, however, is Ash Crimson. He becomes the Villain Protagonist, depowers the much more experienced Chizuru and Iori, brews one HELL of a Batman Gambit and reveals himself as a Good All Along figure via saving the world from Those Of the Past when he gets himself and his ancestor ret goned... while being only in his mid-to-late teens.
Rouge the Bat from Sonic the Hedgehog, who is an expert treasure hunter and government agent despite only being 18.
Little Mac from Punch-Out!! is a teenage boxing genius, plowing through the ranks of the WVBA and beating boxers much taller, bigger and stronger than he is at the impressively young age of 17.
Chihiro Fujisaki of Dangan Ronpa is an extremely talented programmer who was admitted to Hope's Peak Academy for her abilities.
Tedd in El Goonish Shive is a Teen Genius overlapping with Mad Scientist. As time has passed, most of his wacky inventions have been retconned to no longer be his own, edging him out of this trope, but he's still the smartest member of the cast.
He's still managed to adapt the technology a lot and the Aliens who gave it to him in the first place couldn't even begin to fix it, so his genius title remains.
Molly & Galatea in The Inexplicable Adventures of Bob! are both child geniuses, able to perform technological wonders with minimal effort. Considering that they are artificial life forms less than a year old, they are in fact very young. Molly's personality is overtly and unapologetically childlike. Galatea's speech patterns are much more adult-sounding and pretentious, but her naivete still displays her extreme youth.
Just a year out of being a Child Prodigy, Kat Donlan of Gunnerkrigg Court is a thirteen year old Gadgeteer Genius who designed an anti-gravity device at the age of twelve... which she didn't even find that remarkable, instead getting annoyed when the practical purpose of the device was ignored at the school science fair for the anti-grav device itself.
Fernando in Drive is a subversion despite being the head engineer of his ship at 14. He didn't get the job because of an exceptional intellect, but because he's a member of the Royal Family. Only the Familia can service the ship's drive, and they're badly in need of more men.
Dubious Company's Future High Priestess Sal. She is in her late teens and is easily one of the smartest characters in the comic's universe.
Implied; Annie Chang of Pulse, the 20 year old Wrench Wench engineer has been designing robots and artificial limbs for years. Before her career as a superhero, she repaired equipment at her Superhero School.
Several in Homestuck, considering most of the cast are thirteen years old. Equius builds robots. Terezi is a skilled manipulator. Jade is a prophet pulling through several StableTimeLoops. And Dave manages to keep track of several said time loops in his head. (Granted, he does have help from Terezi.)
While the Alpha kids are about 16, they still count. Dirk is an accomplished roboticist who designed an AI that very nearly passes the Turing Test. Roxy is a hacker and possibly the only protaganist to come close to Nannasprite's knowledge about Betty Crocker. Jake built Liv Tyler, aka the Uber-Bunny and he's only the third most talented roboticist. Jane hasn't quite shown her credentials yet, but she is the heiress to a multi-global empire.
The most notable example from the Global Guardians PBEM Universe is The Evil Mastermind, leader of Evil Mensa. He's only twelve years old. He is also the third smartest person on the planet, and has already put together his own Criminal Conspiracy that's about an inch away from controlling all crime in Manhattan.
A good number of the exemplar kids also qualify, due to that nifty "exemplar mental package;" Stopwatch (a Crazy-PreparedClock King type) comes to mind, as does Diamondback, who has been alluded to as having one of the highest IQ's in the freshman class, if not the whole school. Also Ayla, naturally; he's a teen financial genius, having been learning the ways of business and high finance roughly since he was able to talk.
Jobe Wilkins, who is not only a frighteningly powerful bio-devisor but also has scads of patents in biological areas. He just developed a cure for dysentery. Problem? He's an amoral monster with all the empathy of a tarantula.
Kairan Fisher from Chronicles of Syntax is only eighteen, but is amazing with technology. Daynah is this as well, though no specific age is mentioned. They meet at a school for gifted students.
In Daria, the titular character, Jane Lane and Thomas "Tom" Sloane. Jodie Landon as well, who was once selected along side Daria as possible candidates for a school for gifted intelligence.
Batman Beyond: Maxine "Max" Gibson, who acts as Terry's Secret Keeper, tutor, and Alfred. She is also a strategist and thoroughly understands tech. There's also that highest-scoring student in the school thing.
Twilight Sparkle is quite possibly the most powerful non-deity-tier being to ever exist.
Applejack is the undisputed strongest mare in Ponyville, due to her job bucking apples.
Rainbow Dash is likely the best and fastest flyer in Equestria, probably even better than the Wonderbolts themselves.
Rarity's dresses amaze fashion veterans.
Fluttershy can calm any animal, be it a raging dragon to freakin' Cerberus.
Pinkie Pie make just about anyone smile, and throws the best parties in Ponyville.
John Stuart Mill was raised by his economist father John Mill and philosopher Jeremy Bentham (each of whom was a genius in his own right) as an experiment for Bentham's ideas on education and to create the genius they needed to carry on their work in utilitarianism and ethics. J. S. Mill could read Greek by the age of three, and he was so well-versed in economics and political theory that he was editing and writing his father's textbooks by the age of eleven. He had a nervous breakdown by the age of twenty, but eventually recovered.
Scottish mathematician Colin Maclaurin was in the University of Glasgow by 11, and had his master's degree at 15.
George Hotz - aka, geohot - unlocked the iPhone during his summer vacation.
Growing up in the Caribbean, Alexander Hamilton was so brilliant that his employer trusted him to run his import-export business for months at a stretch. He was either 15 or 17 at the time, depending on whether or not he'd lied about his age to improve his employment prospects.
William James Sidis could read the New York Times at 18 months and earned his Bachelor of Arts degree at Harvard University, cum laude, at age 16.
Later popularly reported as suffering a "burnout", the evidence points to his just getting fed up with being put on public exhibition all the time. After his death a friend wrote that he "had one great cause — the right of an individual in this country to follow his chosen way of life".
Kim Ung-Yong of Korea was said to have a Terman IQ of 210. He started out as a Child Prodigy. He was hired by NASA at age twelve and worked for them until he was eighteen, in a job he later called incredibly boring. Returning to Korea he now teaches civil engineering.
French mathematician and physicist Blaise Pascal started to manifest his talents when he was 9 years old, and grew to be an accomplished scientist by the age of 19.
Benjamin Franklin. He wrote lively and entertaining letters for his brother's newspaper -until said brother found out who was contributing them. After moving to Philadelphia, he eventually began helping Thomas Denham as a clerk, bookkeeper, and shopkeeper.
In the Philippines, there are high schools specifically designed for geniuses in science and technology. In Metro Manila, there's one in almost every city, but there's also the Philippine Science High School, which spans nationwide. And every high school graduate in the countrys enter college at 16, at least until the K-12 program is implemented nationwide.
Frederic Chopin composed his first rondo at age 15.
German Field Marshal Erwin Rommel, at the age of fourteen, was building and piloting his own gliders, as well as dismantling and rebuilding motorcycles.
Not a teen for much longer, but here for your viewing, one Taylor Wilson. He built a working fusor at 14 This kid is going places, and places that either charge high tuitions or pay astronomical salaries (or both).
Tom Lehrer, of all people, earned a bachelor's degree in math from Harvard at the ripe old age of 19.
Weird Al graduated high school at 16, as Valedictorian.